A fuel cell is an apparatus which generates electrochemical reaction in a membrane electrode assembly (hereinafter, referred to as “MEA”.) comprising an electrolyte layer (hereinafter, referred to as “electrolyte membrane”.) and electrodes (i.e. an anode catalytic layer and a cathode catalytic layer) arranged on both sides of the electrolyte membrane, and which extracts electrical energy generated by the electrochemical reaction to outside. Among various fuel cells, solid polymer electrolyte fuel cell (hereinafter, referred to as “PEFC”.) used for domestic cogeneration system, automobiles, and so on can be actuated in a low temperature region. Because of its high energy conversion efficiency, short start-up time, and small-sized and lightweight system, the PEFC has received attention as a power source of a battery car or a portable power supply.
A unit cell of the PEFC comprises a MEA and a pair of current collectors (separators) sandwiching a stacked body including the MEA; the MEA contains a proton conductive polymer which has proton conductivity. During the operation of PEFC, a hydrogen-containing gas (hereinafter, referred to as “hydrogen”.) is supplied to the anode; meanwhile, an oxygen-containing gas (hereinafter, referred to as “air”.) is supplied to the cathode. The hydrogen supplied to the anode is separated into proton and electron under the action of catalyst contained in the anode catalytic layer; the proton generated from the hydrogen reaches the cathode catalytic layer through the anode catalytic layer and the electrolyte membrane. On the other hand, the electron reaches the cathode catalytic layer through an external circuit; by having such a process, it is possible to extract the electrical energy. Then, the proton and the electron both reached the cathode catalytic layer react with oxygen contained in the air which has been supplied to the cathode catalytic layer to produce water under action of catalyst contained in the cathode catalyst layer.
By keeping soaking the proton conductive polymer contained in the MEA with water, it is possible to reduce the proton conductive resistance. Because of this, during the operation of PEFC, it is necessary to keep soaking the MEA with water. However, when water of which amount exceeds the drainage capacity of the unit cells is produced during the operation of the PEFC, liquid water is accumulated in, for example, passages where hydrogen and air to be supplied to the MEA are passing through (hereinafter, it may be merely referred to as “passage”.), which becomes a state called flooding. When flooding occurs, frequency of electrochemical reaction decreases due to the inhibition of diffusion of the reaction gases; thereby power generation performance of the PEFC declines. Hence, so as to improve the power generation performance of the PEFC, it is necessary to prevent the occurrence of flooding.
As an art to prevent the occurrence of flooding, so far, PEFCs having passages of which inlet port or outlet port is obstructed have been developed. With the mode having the obstructed passages, it is possible to diffuse a larger amount of reaction gases even in a region of the stacked body facing a portion of a separator located between the adjacent passages (hereinafter, referred to as “projection portion”.). Accordingly, by this mode, it is possible to improve the drainage performance.
For example, Patent document 1 discloses an art regarding PEFC having an obstructed passage. The Patent document 1 discloses an embodiment where the number of the obstructed passage (hereinafter, the obstructed passage may be referred to as “inlet passage”.) through which gasses to be supplied to the MEA pass and the number of the obstructed passage (hereinafter, the obstructed passage may be referred to as “outlet passage”.) through which the gasses having been passed through the MEA pass are the same.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 11-016591